In connection with the determining and/or monitoring of process quantities in process automation, the trend is increasingly in the direction of making available to the user, besides the actual measured value of, for example, flow, e.g. flow rate, pressure, fill level, temperature, conductivity, or ion concentration, also information concerning current or future functionality, or remaining service life, of the measuring device under the reigning system and/or process conditions. Current catchwords in this connection are ‘predictive maintenance’, ‘advanced diagnostics’ and ‘meantime before failure’. Goal of these efforts is, in the end, to prevent, or reduce to a minimum, measuring-device down-time and to increase the quality of the delivered, measured values.